1. Field of the Invention
The invention relates to the field of implantable cardiac stimulation devices and to improved systems and methods of adjusting implantable devices for individual patients.
2. Description of the Related Art
Numerous patients suffer from disease conditions that affect their cardiac performance. For example, diseased myocardium reduces the mechanical pumping capabilities of the heart. Damaged valves can limit the sealing capabilities of the heart reducing capacity for complete filling and/or emptying. Impaired conduction and/or abnormalities in intrinsic activation can result in inappropriate/impaired stimulation of the cardiac tissue.
Implantable cardiac stimulation devices have been developed to provide therapy for certain patients suffering impaired cardiac function. Implantable cardiac stimulation devices generally include an implantable stimulation pulse generator and a microprocessor based controller regulating operation of the device. Implantable cardiac stimulation devices also typically include one or more implantable leads which are configured for implantation to extend adjacent the patient's heart. The implantable leads typically include one or more electrodes. The electrodes can be configured for dedicated sensing or delivery of stimulation or can be configured for combined sensing and stimulation delivery functions. The implantable devices are generally adapted to automatically sense the patient's physiologic status and automatically generate and deliver stimulation for cardiac abnormalities.
As one example, implantable cardiac stimulation devices have been designed to improve congestive heart failure (CHF) symptoms in certain cardiomyopathy patients with electromechanical dysynchrony. As such devices are adapted to provide therapy to attempt to resynchronize the patient's cardiac activity, for example, ventricle-ventricle synchrony, such devices are frequently referred to as cardiac resynchronization therapy (CRT) devices. Existing CRT devices do not necessarily have algorithms or capacity for adjusting or optimizing interval timing between pacing stimuli in different locations. Many physicians implant CRT devices without modification of default programmed interval timing. Thus, existing CRT devices generally pace the right ventricle (RV) and the left ventricle (LV) simultaneously or at a fixed delay therebetween.
While such CRT devices have been shown to benefit a number of CHF patients, there remain a significant proportion of patients who exhibit substantially less beneficial response to existing cardiac resynchronization therapies. Thus, it will be understood that there exists a need for improved therapies, for example, improved designs of implantable stimulation devices and improved methods of operating existing implantable cardiac therapy device designs to extend beneficial therapies to a broader range of patients.